Package org.apache.groovy.runtime.async

Class FlowPublisherAdapter

java.lang.Object

org.apache.groovy.runtime.async.FlowPublisherAdapter

All Implemented Interfaces:

AwaitableAdapter

public final class FlowPublisherAdapter
extends Object
implements AwaitableAdapter

Adapter for Flow.Publisher, the JDK's built-in Reactive Streams type. Enables:

• await publisher — completes with the first onNext value, then cancels the subscription. Completes with null if the publisher signals onComplete without emitting.
• for await (item in publisher) — iterates over emitted values with bounded backpressure (see DEFAULT_BATCH_SIZE).

Conformance:

• Reactive Streams §2.13: onNext(null) is treated as a protocol violation and surfaced as a NullPointerException.
• A second onSubscribe after the first is cancelled.
• Signals after a terminal onError/onComplete are ignored.

This adapter is registered as the lowest-priority built-in (after SPI-loaded adapters) so framework-specific adapters (Reactor, RxJava) take precedence for their concrete types.

Since:

6.0.0

Field Summary

Fields

Modifier and Type	Field	Description
static final int	DEFAULT_BATCH_SIZE	Default request batch size for for await iteration.

Constructor Summary

Constructors

Constructor	Description
FlowPublisherAdapter()

Method Summary

Modifier and Type	Method	Description
boolean	supportsAwaitable(Class<?> type)	Returns true if this adapter can convert instances of the given type to Awaitable (single-value async result).
boolean	supportsIterable(Class<?> type)	Returns true if this adapter can convert instances of the given type to an Iterable for for await loops.
<T> Awaitable<T>	toAwaitable(Object source)	Converts the given source object to an Awaitable.
<T> Iterable<T>	toIterable(Object source)	Converts the given source object to an Iterable.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

DEFAULT_BATCH_SIZE

public static final int DEFAULT_BATCH_SIZE

Default request batch size for for await iteration. Chosen as a compromise between throughput (larger = fewer request() calls) and memory (larger = bigger in-flight buffer). Override per-call by wrapping with a custom adapter if needed.

See Also:

• Constant Field Values

Constructor Details

FlowPublisherAdapter

public FlowPublisherAdapter()

Method Details

supportsAwaitable

public boolean supportsAwaitable(Class<?> type)

Description copied from interface: AwaitableAdapter

Returns true if this adapter can convert instances of the given type to Awaitable (single-value async result).

Specified by:

supportsAwaitable in interface AwaitableAdapter

supportsIterable

public boolean supportsIterable(Class<?> type)

Description copied from interface: AwaitableAdapter

Returns true if this adapter can convert instances of the given type to an Iterable for for await loops. Defaults to false; override for multi-value async types (e.g., Reactor Flux, RxJava Observable).

Specified by:

supportsIterable in interface AwaitableAdapter

toAwaitable

public <T> Awaitable<T> toAwaitable(Object source)

Description copied from interface: AwaitableAdapter

Converts the given source object to an Awaitable. Called only when AwaitableAdapter.supportsAwaitable(java.lang.Class<?>) returned true.

Specified by:

toAwaitable in interface AwaitableAdapter

toIterable

public <T> Iterable<T> toIterable(Object source)

Description copied from interface: AwaitableAdapter

Converts the given source object to an Iterable. Called only when AwaitableAdapter.supportsIterable(java.lang.Class<?>) returned true. The returned iterable typically blocks on next() until the next element is available — with virtual threads this is efficient.

Specified by:

toIterable in interface AwaitableAdapter